In 1904 the Quaker mystic and philosopher Rufus Jones published Social Law in the Spiritual World with a grand ambition. “The cure for skepticism,” Jones declared at the outset, “is always deeper knowledge,” and with this book he sought to bring deeper knowledge to a new generation of modern skeptics. Like many intellectuals of his day, Jones knew firsthand the struggle of the modern believer, as he had grappled first with Darwinian evolution and then with the even more unsettling theories of modern psychology. “There are few crises to compare,” he noted, based on this experience, “with that which appears when the simple, childhood religion, imbibed at mother’s knee and absorbed from early...